improving the performance of solar pv system with sepic · lark do” soft-switching sepic...

IMPROVING THE PERFORMANCE OF

SOLAR PV SYSTEM WITH SEPIC 1K.Lakshmi Deepak,

KLUniversity, Department of

Electrical and Electronics

Engineering, Vijayawada,

India.

2G.Pavan Kumar,

KLUniversity, Department of

Electrical and Electronics

Engineering, Vijayawada

India.

3P.Tripura, KLUniversity,

Department of Electrical and

Electronics Engineering,

Vijayawada, India.

Abstract---- Solar module is considered as

fundamental power transformation unit of

Photovoltaic (PV) generation system. The

performance of a PV array strongly depends on

operating environmental conditions such as

operating temperature, solar insolation, shading

array configuration. Often PV arrays get shadowed

fully or partially by passing cloud, building, poles,

trees, etc. Under such partial shading conditions,

the operation of PV arrays get more complicated

with more than one peak and it is very important to

predict the characteristics to obtain possible

maximum power. In this paper a modified DC-DC

converter is presented for maximum power point

tracking (MPPT) with PI controller to improve the

performance of PV system. The

MATLAB/SIMULINK power system tool box will

be used to stimulate the proposed system.

Keywords----MATLAB/Simulink, Photovoltaic

arrays, Shading effect, DC-DC Converter.

1. INTRODUCTION

Solar energy is the one of the best

renewable energy for future applications .So the

use of photo voltaic (PV) systems increased with

reduced costs and increased efficiency. But the

generation of electricity from photo voltaic (PV)

system is more expensive than the other non-

renewable energy sources. We know that non-

conventional sources which are also known as

renewable energy resources are becoming more

popular now a days as they are available nature

free. Renewable energy sources are defined as the

sources which can be reproduced from nature again

and again once even they used.

There are many advantages with renewable energy

resources comparing to non-renewable energy

source. Some of the advantages are renewable

energy sources are cost free and also pollution free

compared to non-renewable resources. Some of the

main examples for this renewable resources are

solar, wind, tidal etc. Here in this project work we

are considering solar as the source and obtaining

maximum power from the sun by using maximum

power point tracking algorithms (MPPT’s). There

are many algorithms are used for extracting

maximum power such as perturb and observe,

incremental conductance, fuzzy control etc. In our

daily life, power electronic converters have been

widely used, not only for industry applications but

also in many electronic products, such as portable

devices and consumer electronics. Actually, most

electronic devices are not using energy directly

from the power system or a battery set. To provide

the required voltage or current level to a load, in

general, a power electronic converter is interposed

between the power source and the load to perform

the conversion of the voltage or current level and in

addition to regulate the power requirement.

A conventional power electronic converter

is supplied from a single input source, but may

provide multiple outputs. In the case that two or

more voltage or current levels are required by the

loads, a transformer with multiple output windings

is employed [1], [2]. On the other hand, however,

for some applications, the loads may not be

powered from a single source but from two or more

input sources specified by different voltage,

current, and power ratings [3-13]. For example, a

solar power based street lamp is mainly supplied

from solar cells, but needs a subordinate battery

power.

SOLAR PHOTOVOLATIC SYSTEM:

a. Photovoltaic Array Modeling:

In the PV network of electrical

phenomenon, cell is the necessary part. For the

raise in appropriate current, high power and

potential difference, the sunlight dependent cells

and their region unit joined in non-current or

parallel fashion called as PV exhibit are used. In

practical applications, each and every cell is similar

to diode with the intersection designed by the

semiconductor material. When the light weight is

absorbed by the electrical marvel sway at the point

of intersection, it gives the streams at once. The

(current-voltage) and (Power-Voltage) attributes at

International Journal of Applied Engineering Research ISSN 0973-4562 Volume 12, Number 1 (2017) © Research India Publications. http://www.ripublication.com

606

absolutely unpredictable star intensities of the PV

exhibit are represented in figure 3, whereas the

often seen existence of most electrical outlet on

each yield is shown in power diagram 2.

I = Iph – ID -Ish (1)

I=Iph –Io [exp (q V D / nKT)] – (vD /RS) (2)

Figure 1: PV Electrical Equivalent circuit

Solar cell output power is given as the product of V

and I

Figure 2: Response of output characteristics of PV Array

DC-DC CONVERTER:

A. BOOST CONVERTER A boost converter is one of the DC-DC

converter. Which is used for increasing the output

voltage? The name itself says that its main function

is boosting operation. Boosting means stepping up

i.e. increasing the output. Buck-Boost converter

also one of the type of Boost converter but it is the

combination of both Buck and Boost means it is

capable of doing both step up and step down

operations. But there are some disadvantages of

these converters those are, Buck-Boost converters

suffer from high amount of input ripple. These

ripples create harmonics. The CUK and Buck-

Boost converters operation causes large amount of

electrical stress on components this can lead to

device failure or overheating. The diagrammatic

representation of Boost type converter is shown in

the figure which contains semiconductor devices,

and inductor, capacitors which acts as filters to

reduce the amount of ripples at the output side.

Figure: 3 Shows the circuit design of DC-Dc converter

PERTURB AND OBSERVE MPPT

ALGORITHM:

In this type of MPPT algorithm requires

external circuit to repeatedly perturb the array

voltage and subsequently measure the resulting

change in the output power. The main disadvantage

of this algorithm is it forces the system to oscillate

around MPP instead of continuously tracking it.

This algorithm fails under rapidly changing

environment. The major disadvantage of P&O

algorithm is during rapid fluctuations of insolation

the algorithm is likely to lose its direction while

tracking true MPP. So that is this algorithm is not

preferable under rapidly changing environmental

conditions. The advanced version P&O is

incremental conductance algorithm it is designed to

overcome the drawbacks of P&O algorithm under

rapidly changing environmental conditions in this

algorithm the increase and decrease operations are

performed continuously to achieve maximum

power point in one direction. The output is

continuously compared with previous to have better

output.

Figure 4: Flow Chart representation of P&O Technique


607

Mathematical Modelling of PV System:

PV cells are grouped in larger units

called PV modules which are further

interconnected in a parallel-series configuration

to form PV arrays.

The photovoltaic panel can be modelled

mathematically as given in equations

Modulo-Photo Current Can be expressed as:

Module reverse saturation current – Irs

The module saturation current I0 varies with the

cell temperature, which is given by

The PV output Current is given as,

SIMULATION RESULTS:

Here in this project work a real time organisation

was taken for analysis and developed under DC-

DC converter such as SEPIC.

A block diagram of the stage by stage model based

upon the equations of PV model is represented in

Simulink environment as given in Figures 5 to 10.

These models are developed in moderate

complexity to include the temperature dependence

of the photo current source, the saturation current

through the diode, and a series resistance is

considered based upon the shackle diode equation

as shown in above section.

Figure 5: Model for ISC at a given temprature

Figure 6: Model for reverse saturation current

through the diode

Figure 7: Model takes reverse saturation current,

module reference temperature and the module

operating temperature as input and calculates

module saturation current

Figure 8: Model takes operating temperature in

Kelvin and calculates the product NsAkT


608

Figure 9: Model executes the function given by

equation IPV

Figure 10: Model contains all the six model

interconnected together

Figure 11: Simulation model for PV array with

shading effect

Figure 12: Simulation model for PV array with

shading effect under DC-DC Converter

Figure 13: Simulation result for I-V Characterstics

without Shading Effect

Figure 14: Simulation result for P-V Characterstics

without Shading Effect

Figure 13: Simulation result for I-V Characterstics

with Shading Effect (3-pannels)

Figure 14: Simulation result for P-V Characterstics

with Shading Effect (3-pannels)


609

Figure 15: Simulation result for Output Voltage

from Converter

Figure 15: Simulation result for Output Power from

Converter

CONCLUSION

A Matlab/Simulink model for the solar PV

cells, modules, and array is developed and

presented in this paper. This model is based on the

fundamental circuit equations of a solar PV array

taking into the effects of physical and

environmental parameters such as cell temperature,

solar irradiation and shading condition. As a result

of the study, the proposed model seems to be easy

for other researchers to follow to build the model

and study by themselves because it is based on the

Equations from the mathematical modelling. In

addition, the proposed model is also used

effectively to study the effect of shadow on

operating characteristics of solar PV system with

DC-DC converter for improving the output power.

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